You should probably look at lowering those numbers to around 4 - 6 ... as neither army in any theater had more than 300 cannon. 300 may actually be the number of artillerists, but that's not the way the artillery units count numbers.

On Windows 10, right click the speaker icon in the lower right of your task bar.
There should be an option to troubleshoot sound issues.
The option for playback devices should list all your available sound outputs. Clicking on the device that's checked will allow the "Properties" bar to become available, clicking on that will provide more information regarding your system.
Also in the lower right is an up carat (^) left clicking that will provide a box full of icons, you should be able to locate another speaker type icon, mousing over that will display your sound system, (mine says Realtek HD Audio Manager), right clicking on that speaker will display a dialog box that will allow you several options, one of those options will allow you to select 7.1 or 5.1 configurations.

You might want to re-think this.
Johnston was wounded in the battle of Seven Pines/Fair Oaks, day two, (June 1st 1862.) Davis appointed Maj Gen Gustavus Smith, Johnston's second in command, to manage the Army. That lasted a whole day when Smith did a whole lot of nothing to follow up the Fair Oaks/Seven Pines battle. On June 2nd Davis appointed Robert E Lee in command and he immediately took to living in the field. He was a field commander from the first of his appointment. His field headquarters are all plainly indicated in all battles from the day he was given command.
Those battles started with some skirmishing on the prior fields of Fair Oaks and Oak Grove on the south bank of the Chickahominy River, before he devised his right wing flanking movement that started the Seven Days Battles involving Mechanicsville, Gaines Mill, Savage Station, Glendale, then Malvern Hill ... and on for the rest of the war.
Lee had an extremely interesting career with the Confederacy to start with, being sent to such places as South Carolina, then to command the forces in the Ohio Valley, (where he actually retreated from forces under McClellan's command,) to the eventual desk job you mention, as President Davis' assistant before being appointed to command the Confederate forces.

Not so much "a lack of interest" as it is, this group was very active during the design phase of the game, but I've now noticed that since it's gone "finished" the activity on this site, and likely with the game, has slowed quite a bit.
That said, I have just finished a campaign and didn't want to implement your mods/changes in the middle of what I was doing.
I think if you can reply to @Aetius with as much information as requested it would / could help others to understand as well.
Frankly, myself, I'm a realism kinda guy, I would love to recreate battles as they happened with casualties being more comparable to reality, and not this outlandish and crazy numbers applied in the game.
But I suppose that would require a complete rewrite of the AI.

Be careful, do not confuse two different ammunitions as one or the same. Canister did not require an internal charge as Case did.
There are limits when it is appropriate to use one or the other. And while there are stories (reports,) out there where in desperate situations, fusing were removed from Case, there are inherent danger in doing so.